Wireless networks, multimedia techniques and the Internet are integrated, and so demands are increasing for types and quality of wireless communication operations. In order to satisfy requirements for wireless multimedia and high-speed data transmission, development of new-generation wireless communication systems is demanded. Among the systems, MIMO (Multi-Input Multi-Output) wireless transmission techniques attract a widespread attention.
By employing the MIMO technique, it is possible to obtain a space diversity and multiplex gain. Further, in the MIMO technique, when the number of receiving antennas is equal to greater than the number of transmitting antennas, there is a linear relationship between the MIMO channel capacity in Rayleigh fading and the number of transmitting antennas. The MIMO technique makes it possible to significantly increase system capacity without consuming extra power and bandwidth and furthermore remarkably improve transmission link quality. Accordingly, the MIMO technique is suitable for multimedia operations with high transmission rates such as audio, video and the like.
FIG. 1A is a block diagram showing a configuration of a conventional MIMO transmitting apparatus. FIG. 1B is a block diagram showing a configuration of a conventional MIMO receiving apparatus. The transmitting side and receiving side each have Nt transmitting antennas 106 and Nr receiving antennas 108. On the transmitting side, an input information bit sequence is outputted to coding module 101. Coding module 101 carries out error correction coding on the bit sequence such that robustness to noise is provided. The encoded bit sequence is outputted to modulation module 102. Modulation module 102 carries out digital modulation on the encoded sequence. The above operation is mainly carried out in a baseband section of the transmitter. The modulated baseband code is outputted to a radio section on the transmitting side. In the radio section, first, frequency synthesizer 107 generates a carrier signal required at mixer 103. The generated signal is outputted to mixer 103. The radio section carries out carrier modulation on the baseband input signal. The carrier-modulated signal is outputted to pulse forming filer 104. Pulse forming filter 104 carries out pulse forming processing on a transmission code. Finally, power amplifier 105 amplifies signal power. Then, the amplified signal is transmitted on the channel.
On the receiving side, low-noise amplifier (LNA) 109 amplifies a received carrier signal. The amplified carrier signal is inputted to filter 110. Filter 110 carries out filtering processing on the input signal. Mixer 111 down-coverts the carrier signal into a baseband signal. Intermediate-frequency amplifying filter 112 amplifies and filters the down-converted signal. Then, the amplified and filtered signal is inputted to baseband signal detecting section 113. Baseband signal detecting section 113 divides transmission signals of antenna branches. Demodulating section 114 demodulates the code to a bit sequence. Decoding section 115 decodes the demodulated bit sequence to an information bit sequence.